儿茶素对肌原纤维蛋白氧化、结构及凝胶特性的影响

采用羟自由基氧化体系（10 μmol/L FeCl3、100 μmol/L VC和1 mmol/L H2O2）研究不同添加量儿茶素（10、50、100、150 μmol/g）对肌原纤维蛋白氧化、结构及凝胶特性的影响，同时以未氧化和氧化后未添加儿茶素（0 μmol/g）肌原纤维蛋白作为对照组，对肌原纤维蛋白羰基含量、总巯基含量、表面疏水性、溶解度、粒径分布、凝胶强度、凝胶保水性及肌原纤维蛋白流变特性进行测定，并观察凝胶微观结构。结果表明：添加儿茶素能减少羰基化合物的产生，但添加量过高会促进肌原纤维蛋白氧化；与未氧化和未添加儿茶素组相比，添加儿茶素降低了肌原纤维蛋白表面疏水性；随着儿茶素添加量增加，肌原纤维蛋白巯基含量逐渐降低，溶解度显著降低，粒径逐渐增大，凝胶强度和保水性逐渐下降，凝胶微观结构更加疏松多孔，蛋白胶束聚集，中、高添加量（50、100、150 μmol/g）儿茶素使得肌原纤维蛋白失去典型的流变曲线。中、高添加量儿茶素与肌原纤维蛋白发生共价交联，并导致肌原纤维蛋白发生疏水性聚集，最终削弱了肌原纤维蛋白的凝胶特性。

Effect of Catechin on the Oxidation,Structure and Gel Properties of Myofibrillar Protein

The effects of different concentrations of catechin (10, 50, 100 and 150 μmol/g proteins) on the oxidation, structure and gel properties of myofibrillar proteins were studied. Oxidation was carried out in a hydroxyl radical oxidation system (10 μmol/L FeCl3, 100 μmol/L VC and 1 mmol/L H2O2). Non-oxidized and oxidized myofibrillar proteins without added catechin were used as control groups. The carbonyl content, total sulfhydryl content, surface hydrophobicity, solubility, particle size distribution, gel strength, water holding capacity and rheological properties of all samples were determined, and the microstructure of heat-induced protein gel was observed. The results showed that catechin could reduce the production of carbonyl compounds, but at high concentration promote the oxidation of myofibrillar proteins. Compared with the control groups, catechin decreased the surface hydrophobicity. With increased concentration of catechin, the sulfhydryl content decreased gradually, the solubility declined significantly, the particle size increased and the gel strength and water-holding capacity fell gradually. The gel microstructure became more loose and porous and the protein micelles were aggregated. Medium and high concentrations of catechin (50, 100 and 150 μmol/g) caused the protein to lose its typical rheological behavior. In conclusion, high and medium concentrations of catechin could covalently cross-link with myofibrillar proteins and cause the hydrophobic aggregation, ultimately weakening the gel properties of myofibrillar proteins.